A semiconductor device for power conversion used for an inverter control of a motor has a vertical semiconductor element such as an Insulated Gate Bipolar Transistor (IGBT), a Metal-oxide-semiconductor Field-effect Transistor (MOSFET), and a diode. A metalized electrode is formed in a front surface and a rear surface of the semiconductor element, in case of a general semiconductor device, a rear surface electrode located in the rear surface of the semiconductor element and a circuit substrate are connected with a solder joint part therebetween.
Since an amount of heat generation in the semiconductor element tends to increase, a high heat resistance performance is desired for a joint material used for the semiconductor device for power conversion. However, a lead-free solder material having the high heat resistance performance is not currently found, thus considered is that a sinter bonding technique using a sintering phenomenon of a metal grain is applied to the semiconductor device for power conversion as a technique of joining the material replaced with the solder joint. A sinter bonding material used for the sinter bonding technique is made up of a metal grain and an organic constituent. The sinter bonding technique indicates a technique of performing a junction with a joined member using a porous joint layer formed by the sintering phenomenon of the metal grain included in the sinter bonding material.
In a conventional semiconductor device, the rear surface electrode of the semiconductor element is joined to the circuit substrate using a sinter bonding material including silver (Ag) nanoparticle (refer to Patent Document 1, for example).
In another conventional semiconductor device, a high hardness particle made of one of copper (Cu) or Nickel (Ni) or both Cu and Ni, containing the Ag nanoparticle as a main constituent, is dispersed to the sinter bonding material to enhance the intensity of the joint layer at a time of joining the rear surface electrode of the semiconductor element to the circuit substrate (refer to Patent Document 2, for example).